KR20070096852A - Optical glass, precision press-molding and process for the production thereof, and optical element and process for the production thereof - Google Patents

Abstract

An optical glass is provided to have both low-temperature softening characteristics suitable for a precise press molding having a high index of refraction, an excellent glass stability, a low glass transfer temperature and excellent glass stability suitable for hot molding of a preform. An optical glass comprises: 13-30wt% of B2O3, 0.1-4wt% of Li2O, 17-35wt% of ZnO, 15-45wt% of La2O3, 4wt% to less than 15wt% of Ta2O5, 0-10wt% of ZrO2, 0-10wt% of Nb2O5(wherein, a number of Ta2O5/(Ta2O5+ZrO2+Nb2O5) is more than 0.3), 0-20wt% of WO3, and 0-1wt% of Sb2O3; and has a refractive index(eta_d) of 1.80-1.84 and an Abbe's number(v_d) of 40.0-45.0. The sum of Li2O and ZnO ranges from 20% by mass to 35% by mass.

Description

OPTICAL GLASS, PRECISION PRESS-MOLDING AND PROCESS FOR THE PRODUCTION THEREOF, AND OPTICAL ELEMENT AND PROCESS FOR THE PRODUCTION THEREOF}

1 shows an example of a press apparatus for manufacturing the optical element of the present invention.

[Patent 1] Japanese Patent Application Laid-Open No. 6-305669

[Patent 2] Japanese Patent Application Laid-open No. Hei 8-217484

The present invention relates to a high refractive optical glass having a low temperature softening property suitable for precision press molding, a preform for precision press molding formed of optical glass and a manufacturing process thereof, an optical element formed of optical glass and a manufacturing process thereof.

Cameras such as high performance and compact image sensing units or digital cameras have aspherical lenses made of high refractive glass. Such lenses are mass-produced by press molding a glass material called a preform into a press mold having a precision processed molding surface, and precisely transferring the molding surface to the glass material.

The press molding is called precision press molding, and it is possible to form the optical functional surface of the optical element by press molding, so that the aspheric surface is inexpensive and high productivity compared to the process of grinding and polishing glass one by one to complete the aspherical lens. Enable mass production of lenses.

Glass for precision press molding with various optical properties has been proposed. Specifically, Japanese Patent Application Laid-open No. Hei 6-305669 and Japanese Patent Application Laid-open No. Hei 8-217484 propose such a glass.

An advantage of precision press molding is that optical devices, which are expensive and time consuming to manufacture by grinding and polishing, can be mass produced at high productivity. When the preform can be produced directly from the molten glass, the process of starting the glass with melting and ending with the optical element can be made more efficient.

In the above process, a molten glass gob having a considerable amount in one preform is obtained, and the glass gob is formed into a preform while cooling the molten glass gob (hereinafter referred to as "hot forming"), The process becomes very productive compared to the process of cutting, grinding and polishing the glass to complete the preform, and there is no glass dust called sludge included in the cutting, grinding and polishing, and the molten glass is wasted It has the advantage that it can be used without containing dust. Therefore, when an expensive glass material is used, a high performance glass material can be used without increasing the cost much.

However, for hot forming the preform, it is required to mold the molten glass mass into the preform without generating any micro defects such as streaes and devitrification. In particular, when the high refractive glass is molded into a preform, the outflow temperature of the molten glass is increased to prevent loss of transparency. In this case, the viscosity of the glass is lowered, making it difficult to mold, or broken volatilization occurs from the hot glass surface, resulting in streaking. On the other hand, when the outflow temperature is lowered, the glass loses transparency. Therefore, in order to stably produce a good quality preform, a material having good glass stability in the high temperature region is required.

SUMMARY OF THE INVENTION An object of the present invention is a high refractive optical glass having low temperature softening property suitable for precision press molding and excellent glass stability suitable for hot forming of a preform, a preform for precision press molding formed from the optical glass, and a manufacturing process thereof; It is to provide an optical element formed of glass and a manufacturing process thereof.

The present invention is to solve the above problems,

(1) B ₂ O ₃ 13-30%, Li ₂ O 0.1-4%, ZnO 17-35%, La ₂ O ₃ 15-45%, Ta ₂ O ₅ 4-15% , 15% excluding), ZrO ₂ 0-10%, Ta ₂ O ₅ / (Ta ₂ O ₅ + ZrO ₂ + Nb ₂ O ₅ )> 0.3, when Nb ₂ O ₅ 0-10%, WO ₃ 0- An optical glass containing 20%, and Sb ₂ O ₃ 0-1% and having a refractive index (n _d ) of 1.80 to 1.84 and an Abbe number (v _d ) of 40.0 to 45.0,

(2) The optical glass according to the item (1), wherein the total amount of Li ₂ 0 and Zn 0 is 20 to 35 mass%;

(3) expressed as mass%, Si0 ₂ 0 to 10%, Gd ₂ 0 ₃ 0 to 6% (except 6%), Y ₂ 0 ₃ 0 to 10%, Yb ₂ 0 ₃ 0 to 10% The optical glass of the said item (1) or item (2) which further contains,

(4) B ₂ O ₃ , Li ₂ 0, ZnO, La ₂ O ₃ , Ta ₂ 0 ₅ , ZrO ₂ , Nb ₂ 0 ₅ , WO ₃ , SiO ₂ , Gd ₂ O ₃ , Y ₂ 0 ₃ , Yb ₂ The optical glass according to the item (3), wherein the total amount of O ₃ and Sb ₂ 0 ₃ is 99% by mass or more,

(5) a preform for precision press molding formed of the glass according to any one of the items (1) to (4);

(6) preliminary formed of the optical glass according to any one of items (1) to (4) in the process of flowing out the molten glass, separating the molten glass mass, and cooling the molten glass mass. A process for producing a preform for precision press molding, comprising the step of forming a glass mass into a molded body;

(7) an optical element formed of the optical glass according to any one of items (1) to (4) above;

(8) heating the preform for precision press molding as described in the above item (5) or the preform for precision press molding produced by the process as described in the above item (6); A process for producing an optical element comprising the step of precision press molding the preform for

(9) a process for producing the optical element according to the item (8), wherein the preform for precision press molding is introduced into a press mold, and the preform for precision press molding and the press mold are heated together to perform precision press molding;

(10) The optical element according to item (8) above, which comprises heating the preform for precision press molding, and introducing the heated preform for precision press molding into a press mold preheated to perform the precision press molding. To provide a manufacturing process.

According to the present invention, a high refractive optical glass having low temperature softening property suitable for precision press molding and excellent glass stability suitable for hot forming of a preform, a preform for precision press molding formed from the optical glass, a manufacturing process thereof, and the glass It is possible to provide an optical element formed therein and its manufacturing process.

1 is a view showing an example of a press apparatus for manufacturing the optical element of the present invention, wherein reference numeral 1 designates an upper mold member, reference numeral 2 designates a lower mold member, and reference numeral 3 designates a sleeve member. 4 denotes a preform, 9 denotes a support rod, 10 denotes a support bed, 11 denotes a quartz tube, 13 denotes a pressurized rod. Denoted by reference numeral 14 denotes a thermocouple.

Preferred embodiments of the present invention are described in the order of the optical glass of the present invention, a preform for precision press molding, a manufacturing process thereof, an optical element, and a manufacturing process thereof.

[Optical glass]

The optical glass of the present invention is expressed in mass%, B ₂ O ₃ 13-30%, Li ₂ O 0.1-4%, ZnO 17-35%, La ₂ O ₃ 15-45%, Ta ₂ O ₅ 4- 15% (except 15%), ZrO ₂ 0-10%, Ta ₂ O ₅ / (Ta ₂ O ₅ + ZrO ₂ + Nb ₂ O ₅ )> 0.3, Nb ₂ O ₅ 0-10%, WO ₃ 0-20%, and Sb ₂ O ₃ 0-1% and have a refractive index n _{d of} 1.80-1.84 and Abbe number (v _d ) of 40.0-45.0.

The Ta ₂ O ₅ / (Ta ₂ O ₅ + ZrO ₂ + Nb ₂ O ₅₎ is a Ta ₂ O _5, ZrO ₂ and Nb ₂ O ₅ Total Ta ₂ O ₅ to the content (sum of the% by weight) of The ratio (mass ratio) of content is shown.

The optical glass of the present invention will be described in detail below. Content of each component and arbitrary additives shown in% are shown with content by the mass% below, and content ratio and the total amount show the ratio and total amount based on mass below.

B ₂ 0 ₃ is an essential component for forming the glass network. When the content of B ₂ O ₃ is less than 13%, the glass stability in the high temperature region is lowered. If this exceeds 30%, it becomes difficult to obtain the intended refractive index. Therefore, the content of B ₂ O ₃ is preferably limited to 13 to 30%. It is preferably in the range of 14 to 29%, more preferably in the range of 15 to 28%.

Li ₂ 0 is an essential component for lowering the glass transition temperature while maintaining high refractive index and imparting low-temperature softening characteristics suitable for precision press molding. When the content of Li ₂ 0 is less than 0.1, it is difficult to obtain the above effect. If it exceeds 4%, the glass stability in the high temperature region is lowered. Therefore, the content of Li ₂ 0 is preferably limited to 0.1 to 4%. It is preferably in the range of 0.5 to 4%, more preferably in excess of 1% and less than 4%, more preferably in the range of 1.1 to 4%, more preferably in the range of 1.1 to 3%.

ZnO is an essential component that lowers the glass transition temperature while maintaining high refractive index, imparts low-temperature softening characteristics suitable for precision press molding, and lowers the melting temperature of the glass. When the content of ZnO is less than 17%, it is difficult to obtain the above effect. If it exceeds 35%, the glass stability in the high temperature region decreases and dispersion increases. Therefore, the content of ZnO is limited to 17 to 35%. It is preferably in the range of 18 to 35%, more preferably in the range of 18 to 32%, more preferably in the range of 18 to 30%.

The total content of Li ₂ O and ZnO in order to realize a glass suitable for precision press molding and hot forming of the preform by maintaining a balance between the reduction of the glass transition temperature and the improvement of the glass stability while maintaining the desired optical properties. Is preferably adjusted to 20 to 35%. May be introduced to Li ₂ O and ZnO with a relatively large amount in order to maintain the stability of glass in good condition, to distribute the content of _{Ta 2 O 5, ZrO 2,} Nb 2 0 5 is necessary, as will be described later.

La ₂ O ₃ is an essential component that increases refractive index and maintains chemical durability while maintaining dispersion in a desired range. When the content of La ₂ O ₃ is less than 15%, it is difficult to calculate the above effect. If it exceeds 45%, the glass stability in the high temperature region is lowered. Therefore, the content of La ₂ O ₃ is limited to 15 to 45%. It is preferably in the range of 20 to 45%, more preferably in the range of 25 to 45%, more preferably in the range of 27 to 45%, and more preferably in the range of 28 to 45%.

Ta ₂ O ₅ is an essential component that functions to increase the refractive index and improve the glass stability while maintaining the dispersion in the desired range. When the content of Ta ₂ O ₅ is less than 4%, it is difficult to calculate the above effect. When the content of Ta ₂ O ₅ exceeds 15%, the glass stability in the high temperature region is lowered. Therefore, the content of Ta ₂ O ₅ is limited to 4 to 15% (except 15%). Within this range, the content of Ta ₂ O ₅ is preferably 6% or more, more preferably 8% or more, and even more preferably 8.5% or more. The upper limit of the content of Ta ₂ O ₅ is preferably 14.5% or less, more preferably 14% or less, and the content of Ta ₂ O ₅ is particularly good within the range of 8.5 to 14%.

Zr0 ₂ acts to increase the refractive index and is a component that improves glass stability when added in an appropriate amount. When the content of Zr0 ₂ exceeds 10%, the glass stability in the high temperature region is lowered, so the content is limited to 0 to 10%. The content of Zr0 ₂ is preferably in the range of 0.5 to 10%, more preferably in the range of 1 to 10%.

Nb ₂ O ₅ acts to increase the refractive index and is a component that improves glass stability when added in an appropriate amount. When the content of Nb ₂ O ₅ exceeds 10%, the glass stability in the high temperature region decreases and the dispersion becomes large, so that the content is limited to 0 to 10%. The content of Nb ₂ O ₅ is preferably in the range of 0.5 to 10%, more preferably in the range of 1 to 10%.

However, _{Ta 2 O 5, ZrO 2,} Nb 2 content of O ₅ is Ta ₂ O _5, ZrO _2, the ratio of content of Nb ₂ O ₅ Ta ₂ for the total content O ₅ of _{[Ta 2 O 5 / (Ta} 2 0 ₅ + ZrO ₂ + Nb ₂ O ₅ )] is adjusted to exceed 0.3. When the said ratio is 0.3 or less, it is difficult to improve glass stability, maintaining a predetermined optical characteristic and reducing glass transition temperature further. 0.4 or more are preferable, 0.45 or more are more preferable, and 0.5 or more is more preferable.

Although the upper limit of the said ratio is 1, 0.9 or less are favorable and 0.8 or less are more preferable. With respect to Ta ₂ O ₅ , ZrO ₂ , and Nb ₂ O ₅ , Ta ₂ 0 ₅ is introduced in a form dispersed in Zr0 ₂ and Nb ₂ 0 ₅ rather than only increasing the content of Ta ₂ 0 ₅ . In this case, glass stability is further improved while imparting predetermined optical properties and low temperature softening properties. To further improve the properties, the content of Ta ₂ 0 _5, and is preferably adjusted so that many more than the content of Zr0 _2, it is more preferably adjusted so that the content of Ta ₂ O ₅ lot than the content of Nb ₂ 0 ₅ .

W0 ₃ increases the refractive index and serves to improve the glass stability when introduced in the proper amount. However, when the content of WO ₃ exceeds 20%, the glass stability is lowered and the glass is colored to a considerable extent, so the content of WO ₃ is limited to 0 to 20%. The content of W0 ₃ is in the range of 1 to 20% is good, the range of 1 to 15% is better, the range of 3 to 14% is better, the range of 4 to 13% is better, and 5 to The range of 13% is better.

Sb ₂ 0 ₃ can be added as a refining agent. When the content of Sb ₂ 0 ₃ exceeds 1%, the molding surface of the press die may be damaged during the precision press molding, so the content of Sb ₂ 0 ₃ is limited to 0 to 1%. The content of Sb ₂ O ₃ is preferably in the range of 0 to 0.5%.

Si0 ₂ improves the glass stability when introduced in an appropriate amount, and has a function of imparting a viscosity characteristic suitable for hot forming of the preform. When the content of Si0 ₂ exceeds 10%, the glass transition temperature is raised, and the refractive index may be lowered. Therefore, the content of Si0 ₂ is preferably limited to 0 to 10%. The content of Si0 ₂ is more preferably in the range of 1 to 10%, more preferably in the range of 1 to 9%, and even more preferably in the range of 2 to 9%.

The quality of the preform in view of manufacturing by hot forming, the ratio of the SiO ₂ content to the total content of SiO ₂ and _{B 2 O 3 [SiO 2 /} (SiO 2 + B 2 O 3)] is at least O.1 Is good, 0.12 or more is better, and more than 0.25 is better.

Gd ₂ O ₃ serves to adjust optical properties, for example, which acts to increase the refractive index. When the content of Gd ₂ 0 ₃ exceeds 6% In the optical glass of the present invention, the glass stability is decreased. Therefore, the content of Gd ₂ O ₃ is preferably limited to 0 to 6% (except 6%). The content of Gd ₂ O ₃ is more preferably in the range of 0 to 5%, more preferably in the range of 0 to 3%, and even more preferably in the range of 0 to 1%. Gd ₂ 0 ₃ may not be introduced.

Y ₂ O ₃ and Yb ₂ O ₃ also serve to adjust optical properties, which serve to increase the refractive index, for example. If these introductions are excessive, glass stability will fall. The content of each of Y ₂ O ₃ and Yb ₂ O ₃ is in the range of 0 to 10%, the range of 0 to 5% is better, the range of 0 to 3% is better, and the range of 0 to 1%. The range is more preferable, so that Y ₂ O ₃ and Yb ₂ O ₃ may not be introduced.

In addition to the above components, TiO ₂ , Bi ₂ 0 ₃ , Ge0 ₂ , BaO, SrO, CaO, Mg0, Na ₂ 0, K ₂ 0 and the like may be introduced.

Ti0 ₂ , Bi ₂ 0 ₃ increase the dispersion and color the glass. It is therefore essential that their respective content should be limited to less than 1%, more preferably less than 0.5%. More preferably they are not included at all.

The object of the present invention can be achieved without introducing GeO ₂ . In addition, since GeO ₂ is a very expensive material, its content is limited to less than 2%, less than 1% is better, and less than 0.5% is better. More preferably, GeO ₂ is not introduced.

BaO acts to improve glass stability and meltability when added in small amounts. However, compared with similarly acting ZnO, BaO has a weaker action of increasing the refractive index and lowering the glass transition temperature, so introducing BaO instead of ZnO is suitable for obtaining a glass having a high refractive index and a low glass transition temperature. Not. Therefore, the content of BaO is preferably limited to the range of 0 to 3%, more preferably limited to 0 to 1%. More preferably, BaO is not introduced.

Sr0, Ca0, Mg0 acts to adjust the optical properties when introduced in small amounts. However, since they act to lower the refractive index, their introduction is not appropriate. Therefore, the content of each of SrO, CaO, and MgO is preferably limited to the range of 0 to 3%, and more preferably to the range of 0 to 1%. More preferably, none of them are introduced.

Na ₂ O and K ₂ 0 increase the meltability and lower the glass transition temperature, but also lower the refractive index. On the contrary, Li ₂ 0 acts to lower the glass transition temperature while maintaining a high refractive index, so it is not appropriate to introduce Na ₂ 0 and K ₂ 0 in place of Li ₂ 0. Therefore, the content of each of Na ₂ 0 and K ₂ 0 is preferably limited to the range of 0 to 5%, more preferably to the range of 0 to 3%, and further to the range of 0 to 1%. It is good, and more preferably none of them are introduced.

In addition to these, it is not preferable to introduce any one of As ₂ O ₃ , PbO, CdO, ThO ₂ , Lu ₂ O ₃ , F. As ₂ O ₃ , PbO, CdO, ThO ₂ are environmentally undesirable substances. In addition, As ₂ O ₃ has a strong oxidizing property, which damages the molding surface of the press die during precision press molding, thereby shortening the life of the mold. When precision press molding is performed in a non-oxidizing gas atmosphere such as a molding gas, PbO is reduced to precipitate on the glass surface and adheres to the forming surface to lower the surface precision of the optical element. Lu ₂ 0 ₃ is an expensive material and adds cost. Therefore Lu ₂ O ₃ is preferably not introduced. Since F has high volatility and generates streaks during hot forming of the preform, it is not preferable to introduce F.

In addition to these, it is appropriate that a substance which causes the coloring of the glass, such as Cu, Cr, and Co, should not be introduced.

B ₂ O ₃ , Li ₂ O, ZnO, La ₂ O ₃ , Ta ₂ 0 in the optical glass of the present invention in order to satisfy the above various properties and obtain a glass more suitable for hot forming and precision press molding of the preform. ₅ , ZrO ₂ , Nb ₂ O ₅ , WO ₃ , SiO ₂ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ and Sb ₂ 0 ₃ have a good total amount of 99% or more, more preferably 99.5% or more It is preferable that it is 100%. In addition, the total amount of B ₂ O ₃ , Li ₂ O, ZnO, La ₂ O ₃ , Ta ₂ 0 ₅ , ZrO ₂ , Nb ₂ O ₅ , WO ₃ , SiO ₂ and Sb ₂ 0 ₃ in the optical glass of the present invention 99% or more is good, 99.5% or more is more preferable, and 100% is more preferable.

The optical glass of the present invention has a refractive index n _{d in the} range of 1.80 to 1.84 and an Abbe number (v _d ) in the range of 40.0 to 45.0. In order to increase the glass stability and at the same time lower the glass transition temperature, the refractive index n _d is in the range of 1.80 to 1.83 is good, the range of 1.80 to 1.82 is better, and the Abbe number (v _d ) is 40.0 to 44.0 The range is preferable, and the range of 40.0-43.0 is more preferable.

The present invention is suitable for obtaining an optical glass having a glass transition temperature of 550 ° C. or less, preferably 545 ° C. or less, more preferably 540 ° C. or less, and more preferably 535 ° C. or less.

In addition, the present invention is suitable for obtaining an optical glass having a light transmittance expressed by the color degree λ ₈₀ of 420 nm. The chromaticity λ ₈₀ is a wavelength at which the spectral transmittance obtained by providing a glass sample having optically polished surfaces opposed to each other in parallel at intervals of 10.0 ± 0.1 mm and injecting light into one of the surfaces vertically becomes 80%. Spectral transmittance is measured within a wavelength of 280 to 700 nm and is expressed as the ratio (I _out / I _in ) of the intensity (I _out ) of the transmitted light to the intensity (I _in ) of the light incident on the sample, and represents the reflection loss on the sample surface. Contains the value to include. The spectral transmittance of the optical glass of the present invention is at least a wavelength range of λ ₈₀ , but 80% in a wavelength range of 700 nm or less. When the glass has a refractive index of 1.80 or more and a coloring degree λ ₈₀ of 420 nm or less, preferably 415 nm or less, an optical element formed of high refractive index glass having no coloration or almost no coloring can be obtained. In addition, since the glass transition temperature is low and the precision press molding of the aspherical lens is facilitated, the optical glass of the present invention is suitable for the lens constituting a high performance and compact image sensing system.

Since the optical glass of the present invention has a specific gravity of less than 5.0, it is easy to stably float the molten glass when it is molded into a preform while allowing the molten glass mass to float on the molding die. Therefore, although the glass has a high refractive index, a high quality preform can be produced with high productivity.

Although optical glass and its preferred embodiments have been described above, some preferred embodiments will be described below by way of example.

(Optical glass 1-1)

B ₂ 0 ₃ 13 to 30%, Li ₂ 0 0.1 to 4%, ZnO 17 to 35% (wherein the total amount of Li ₂ 0 and Zn0 is 20 to 35%), La ₂ 0 ₃ 15 to 45%, Ta ₂ O ₅ 4 to 15% (except 15%), ZrO ₂ 0.5 to 10%, Nb ₂ O ₅ 0.5 to 10% [Ta ₂ O ₅ / (Ta ₂ O ₅ + ZrO ₂ + Nb ₂ O ₅ )> 0.3], WO ₃ 1-20%, SiO ₂ 0-10%, Gd ₂ 0 ₃ 0-6% (except 6%), Y ₂ 0 ₃ 0-10%, Yb ₂ O ₃ An optical glass comprising 0 to 10%, Sb ₂ 0 ₃ 0 to 1%, and having a refractive index n _d of 1.80 to 1.84 and an Abbe number (v _d ) of 40.0 to 45.0.

(Optical glass 1-2)

The optical glass 1-1, the optical glass the content of Gd ₂ 0 ₃ 0 to 5%.

(Optical glass 1-3)

1-1 Optical glass or an optical glass 1-2, of from 1 to 10% of the optical glass content of Si0 _2.

(Optical glass 1-4)

Optical Glass 1-1 to optical glass, and any one of 1 to 3, the optical glass the content of Li ₂ 0 to 4% l.1.

(Optical glass 1-5)

Optical Glass 1-1 to optical glass, and any one of 1-5, the content of Ta ₂ 0 ₅ than 8% but not more than 14%, the optical glass.

(Optical glass 1-6)

The optical glass 1-5, the optical glasses when the content of Ta ₂ 0 ₅ 8.5 to 14%.

(Optical glass 1-7)

1-1 Optical glass and optical glass to any one of _{1-6, Ta 2 0 5 / (} Ta 2 O 5 + ZrO 2 + Nb 2 O 5) The optical glass not less than 0.5 of the ratio.

(Optical glass 1-8)

Optical Glass 1-1 to optical glass, and any one of 1-7, many optical glass than the content of the content of Ta ₂ O ₅ ZrO _2.

(Optical glass 1-9)

Optical Glass 1-1 to optical glass, and any one of 1-9, many optical glass the content of Ta ₂ 0 ₅ than the content of Nb ₂ 0 _5.

(Optical glass 1-l0)

Optical glass and 1-1 to the optical glass of any one of claims _{1-9, B 2 O 3, Li} 2 O, ZnO, La 2 O 3, Ta 2 0 5, ZrO 2, Nb 2 O 5, WO 3, SiO _{2, Gd 2 O 3, Y} 2 O 3, Yb 2 O 3 and Sb ₂ 0 ₃ the total amount of the optical glass not less than 99%.

(Optical glass 1-11)

Optical glass 1-10, the total amount of B ₂ O ₃ , Li ₂ O, ZnO, La ₂ O ₃ , Ta ₂ 0 ₅ , ZrO ₂ , Nb ₂ O ₅ , WO ₃ , SiO ₂ and Sb ₂ 0 ₃ is 99 Optical glass that is at least%.

(Optical glass 2-1)

B ₂ 0 ₃ 13 to 30%, Li ₂ 0 1.1 to 4%, ZnO 17 to 35% (wherein the total amount of Li ₂ 0 and Zn0 is 20 to 35%), La ₂ 0 ₃ 15 to 45%, Ta ₂ O ₅ 8.5-14%, ZrO ₂ 0-10%, Nb ₂ O ₅ 0-10% [where Ta ₂ O ₅ / (Ta ₂ O ₅ + ZrO ₂ + Nb ₂ O ₅ )> 0.3], WO ₃ 0 to 20%, SiO ₂ 0 to 10%, Gd ₂ 0 ₃ 0 to 5%, Y ₂ 0 ₃ 0 to 10%, Yb ₂ O ₃ 0 to 10%, Sb ₂ 0 ₃ 0 to 1% , Optical glass having a refractive index (n _d ) of 1.80 to 1.84 and an Abbe's number (v _d ) of 40.0 to 45.0.

(Optical glass 2-2)

The optical glass is _{2-1, Ta 2 O 5 / (} Ta 2 O 5 + ZrO 2 + Nb 2 O 5) The optical glass not less than 0.5 of the ratio.

(Optical glass 2-3)

2-1, optical glass or optical glass and 2-2, many optical glass than the content of the content of Ta ₂ 0 ₅ Zr0 _2.

(Optical glass 2-4)

Optical Glass 2-1 to optical glass, and any one of 2 to 3, many optical glass the content of Ta ₂ 0 ₅ than the content of Nb ₂ 0 _5.

(Optical glass 2-5)

The optical glasses 2-1 to the optical glass of any one of _{2-4, B 2 O 3, Li} 2 O, ZnO, La 2 O 3, Ta 2 0 5, ZrO 2, Nb 2 O 5, WO 3, SiO 2 , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ and Sb ₂ O ₃ The total amount of the optical glass of 99% or more.

(Optical glass 2-6)

Optical glass 2-5, with a total amount of B ₂ O ₃ , Li ₂ O, ZnO, La ₂ O ₃ , Ta ₂ 0 ₅ , ZrO ₂ , Nb ₂ O ₅ , WO ₃ , SiO ₂ and Sb ₂ 0 ₃ Optical glass that is at least%.

The optical glasses are weighed and combined with oxides, carbonates, sulfates, nitrates, hydroxides, and the like as raw materials to obtain an intended glass composition, and thoroughly mixed and placed these raw materials to prepare a mixture batch. Can be obtained by heating, melting, defoaming, stirring, to obtain a bubble-free molten glass, and molding the glass. In particular, they can be prepared according to known melting methods.

[Manufacturing process of preform for precision press molding and preform for precision press molding]

The preform for precision press molding of the present invention (hereinafter referred to as "preformed body") is formed of the optical glass of the present invention.

The preform is a glass molding material having a mass equivalent to that of a precision press-molded product and having an appropriate shape in accordance with the shape of the precision press-molded product. Examples of such forms include spheres, ellipses, and the like. The preform is heated to have a precision press moldable viscosity before being provided for precision press molding.

The preform of this invention can be equipped with a carbon containing film (preferably carbon film) on the surface as needed.

The manufacturing process of the preform for precision press molding provided by the present invention comprises the steps of flowing out the molten glass, separating the molten glass mass, and preliminary formed of the optical glass in the process of cooling the molten glass mass. Shaping the molten glass mass into a shaped body, which is one of the processes for making the preform of the present invention.

Since the glass constituting the preform has high stability in the high temperature region, the viscosity of the molten glass can be increased when the molten glass flows out, so that the process can produce high quality preforms with high productivity. Has an advantage.

In the manufacturing process of the preform of the present invention, the molten glass flows out of the pipe to separate the molten glass mass and is molded into the preform of any one of the optical glasses during the cooling process of the molten glass mass. However, the manufacturing process of the preform should not be limited to the above process, and the preform of the present invention also provides a glass molding material from the molten glass, cuts or divides the glass molding material, thereby grinding the cut pieces and It can be produced by performing polishing.

In the preform manufacturing process of the present invention in which the molten glass mass is separated, the molten glass is separated to obtain a molten glass mass, so that the mass precision of the preform may be superior to dividing the solidified glass. In addition, since the preform is molded directly from the molten glass mass, glass dust due to cutting, grinding and polishing does not occur. Therefore, the production efficiency is improved and the utilization rate of the glass is improved, so that the manufacturing cost can be kept low even if expensive raw materials are used. In addition, in order to perform cutting, grinding, and polishing, it is necessary to sufficiently reduce the strain of the molded glass, and it is necessary to perform long-term annealing. However, according to the process of the present invention, the annealing time can be shortened.

In the manufacturing process of the preform of the present invention, it is preferable that the preform is molded in a state where the glass mass is suspended by applying a gas pressure to impart a smooth clean surface to the preform. In addition, the preformed body whose surface is formed as a free surface is preferred. Moreover, it is preferable that there are no cutting marks called shear marks. The shear mark is formed when the outflowing molten glass is cut by the cutting blade. If the shear mark remains until the step of obtaining the precision press-formed product, the part becomes a defect. Therefore, it is preferable that there is no shear mark at the preform stage. The method of separating molten glass without using a cutting blade and without forming a shear mark includes a method in which molten glass is dropped from an outlet pipe, a tip of the molten glass flow flowing out of the outlet pipe is supported, A method in which the support is removed at a point in time at which a molten glass mass of weight can be separated (referred to as a "falling-separation method"). In the drop separation method, the molten glass flow may be separated at a narrow portion formed between the leading side of the molten glass flow and the outlet pipe outlet side to obtain a molten glass mass having a predetermined weight. The molten glass mass is then formed into a preform having a form suitable for press molding while in a soft state.

[Manufacturing Process of Optical Device and Optical Device]

The optical element of the present invention is formed from the optical glass of the present invention. The optical element of this invention has a high refractive index low dispersion characteristic like the optical glass of this invention which comprises an optical element.

Optical elements of the present invention include, for example, spherical lenses, aspherical lenses, various lenses such as micro lenses, diffraction gratings, lenses with diffraction gratings, lens arrays, prisms, and the like. In view of the form, the optical element includes, for example, a concave meniscus lens, a double-sided concave lens, a flat lens, a convex meniscus lens, a double-sided convex lens, and a flat convex lens. Preferably, the optical element is an optical element obtained by heating the preform of the present invention and precision press molding.

The optical element may be provided with an antireflection film, a total reflection film, a partial reflection film, a film having spectral characteristics, or the like as necessary.

The manufacturing process of the optical element will be described below.

The manufacturing process of the optical element provided by the present invention comprises the steps of heating the preform for precision press molding of the present invention or the preform for precision press molding produced by the manufacturing process of the preform for precision press molding of the present invention; Precision press molding the preform into a mold.

Precision press molding is also called "Optics molding", which is well known in the art.

The surface of an optical element that transmits, refracts, diffracts, or reflects light rays is called an optical functional surface. For example, the lens surface of the lens corresponds to the optical function surface, such as an aspherical surface of an aspherical lens or a spherical surface of a spherical lens. The precision press molding method refers to a method in which the shape of the molding surface of the press die is accurately transferred to the glass by the press mold so as to form the optical functional surface. That is, precision press molding removes machining such as grinding or polishing to finish the optical functional surface.

Therefore, the manufacturing process of the optical element of the present invention is suitable for manufacturing optical elements such as lenses, lens arrays, diffraction gratings, prisms, and the like, and is particularly suitable for producing aspherical lenses with high productivity.

According to the manufacturing process of the optical element of the present invention, not only an optical element having the above optical characteristics can be manufactured, but also because the preform is formed of an optical glass having low temperature softening characteristics, a relatively low temperature is required for press molding of glass. Since the press can be performed at, the burden on the molding surface of the press die can be reduced, and the life of the molding die (mold release film if the release film is formed on the molding surface) can be extended. In addition, since the glass constituting the preform has high stability, the loss of transparency of the glass can be effectively prevented in the reheating and pressing step. In addition, a series of steps that begin by melting the glass and finish by completing the final product can be performed with high productivity.

Among the high refractive index glass for precision press molding, the optical glass of the present invention has a low glass transition temperature due to using the glass having a relatively high content of Li ₂ O and ZnO. This is advantageous for precision press molding for the production of lenses having negative refractive power, such as concave meniscus lenses, double-sided concave lenses, and flat-cornered lenses. In the press for producing such a lens, the preform is placed in the inner center of the press die, the glass constituting the preform is stretched by the press to form the lens, and the center of the lens has a thickness thicker than the thickness of the peripheral part. Have At this stage, the change in volume distribution of the glass is greater than the change in volume distribution for the lens with positive refractive power. In such molding, a low glass viscosity is set during the press, so that the elongation of the glass during the press is improved. For this purpose, the press temperature is set to a higher temperature. When optical glass having a glass transition temperature of 550 ° C. or lower, preferably 535 ° C. or lower, is used as in the present invention, it is possible to obtain an effect that the wear of the press die is not promoted even if the press temperature is set at a higher temperature.

In addition, the lens having negative refractive power can correct chromatic aberration by the compact configuration combined with the lens formed of highly dispersed glass having positive refractive power.

As a press mold for precision press molding, a known press mold, such as a press mold obtained by forming a mold release film on a molding surface of a mold material such as silicon carbide, cemented carbide, or stainless steel, can be used. The release film may be selected from a carbon containing film, a noble metal alloy film, and the like. The press die also includes an upper die member and a lower die member and, if necessary, a sleeve member. Among them, press molds made of silicon carbide or press molds made of cemented carbide (especially made of cemented carbide containing no binder, for example, WC) in order to effectively reduce or prevent breakage of glass-formed products during press molding. Press mold), and it is more preferable that the mold has a molding surface having a carbon-containing film as a release film.

In the precision press molding method, it is preferable to adopt a non-oxidizing gas atmosphere as the atmosphere during molding in order to keep the molding surface of the press die in a good state. The non-oxidizing gas is preferably selected from nitrogen, a mixed gas of nitrogen and hydrogen. In particular, when a press die having a carbon-containing film on the molding surface is used, or when a press die made of silicon carbide is used, it is appropriate that precision press molding should be performed in the non-oxidizing atmosphere.

Precision press molding particularly suitable for the manufacture of the optical element of the present invention will be described below.

(Precision Press Forming Method 1)

This method is a method in which a preform for precision press molding is introduced into a press mold, the preform and the press mold are heated together, and precision press molding is performed (hereinafter, referred to as "precision press molding method 1").

In the precision press molding method 1, both the press die and the preform are heated up to a temperature at which the glass constituting the preform is at a viscosity of 10 ⁶ to 10 ¹² dPa · s to perform precision press molding.

In addition, before the precision press-formed product is taken out of the press die, the glass is brought to a temperature exhibiting a viscosity of 10 ¹² dPa · s or more, more preferably 10 ¹⁴ dPa · s or more, more preferably 10 ^l6 dPa · s or more. It is desirable to cool the precision press-formed product.

By the above conditions, not only the shape of the molding surface of the press die can be accurately transferred to glass, but also it can be taken without deforming the precision press-molded product.

(Precision Press Forming Method 2)

This method is a method in which a high-temperature precision press molding preform (preheated) is introduced into a preheated press mold to perform precision press molding (hereinafter referred to as "precision press molding method 2"). According to this method, since the preform is preheated before it is introduced into the press die, an excellent optical element can be produced while the cycle time can be shortened and there is no surface defect.

The press die is preferably preheated to a temperature lower than the temperature for preheating the preform. Therefore, by this preheating, the heating temperature of the press die can be controlled to be lowered, so that wear of the press die can be reduced.

In the precision press molding method 2, the preform is preferably heated to a temperature at which the glass constituting the preform has a viscosity of 10 ⁹ dPa · s or less, more preferably 10 ⁹ dPa · s.

The preform is preferable that pre-heated to a floating state, and the glass constituting the preform Do not you fucking 1O ^{5 · 5} to 1O ⁹ dPa · s, and more preferably is 1O ^{5 ·} at least ⁵ dPa · s 1O ⁹ dPa · It is still better to preheat the preform to a temperature exhibiting a viscosity of less than s.

In addition, it is preferable to start cooling of the glass simultaneously with or during the press.

Preferably, the press die is temperature-controlled to a temperature lower than the preheating temperature of the preform, and the temperature at which the glass exhibits a viscosity of 10 ⁹ to 10 ¹² dPa · s becomes a target temperature for temperature adjustment of the press die. Can be.

In this method, the precision press-formed product is preferably cooled to a temperature at which the glass has a viscosity of 10 ¹² dPa · s or more before being taken out of the press mold.

The precision press-molded product (optical element) is taken out of the press die and slowly cooled as necessary. If the article is an optical element such as a lens, the surface may be coated with an optical thin film as necessary.

Such optical elements, such as aspherical lenses, are suitable as parts of high performance and compact image sensing systems, and are suitable for image sensing systems such as digital cameras, digital video cameras, mobile phone mounted cameras, vehicle mounted cameras and the like.

EXAMPLE

The invention will be explained in more detail below with reference to examples.

Tables 1 to 7 show the compositions of the glasses of Examples 1 to 37. These glasses were obtained as follows. Oxides, hydroxides, carbonates and nitrates corresponding to the components of the glass were used as the material of the glass, and these materials were weighed and thoroughly mixed to obtain the compositions shown in Tables 1 to 7 after formation of the glass. The mixture was charged into a platinum crucible, melted in an electric furnace at a temperature of about 1,200 ° C., homogenized by stirring, refined and poured into a preheated mold to a suitable temperature. The injected glass was cooled to the glass transition temperature, and then immediately the glass was placed in an annealing furnace and slowly cooled to room temperature to provide optical glass.

Each optical glass obtained in this manner was measured for refractive index (n _d ), Abbe's number (v _d ), glass transition temperature, sag temperature, specific gravity in the following manner. Tables 1 to 7 show the results.

(1) refractive index (n _d ) and Abbe's number (v _d )

The optical glass obtained after slow cooling at the temperature drop rate of -30 ° C / hour was measured.

(2) glass transition temperature (T _g ) and yield temperature (T _s )

Optical glass was measured by a thermomechanical analyzer supplied by Rigaku Corporation at a rate of temperature rise of 4 ° C./min.

(3) specific gravity

Optical glass was measured by the Archimedes method.

The preform is molded into a purified, homogeneous molten glass that corresponds to the glass composition shown in Examples 1 to 37 below. The molten glass stably flows out at a constant rate from a pipe made of a platinum alloy whose temperature is adjusted to a flowable temperature range without loss of transparency, and the molten glass mass is dropped by a dropping method. Or separated from the glass flow by a falling separation method, received by a receiving mold having a gas blowing port at the bottom, and blowing gas from the gas blowing port to float the glass mass. It was molded into a preform for precision press molding. By adjusting and controlling the separation interval of the molten glass mass, spherical preforms and flat spherical preforms were obtained.

The preform thus obtained was precision press formed by the press apparatus shown in FIG. 1 to provide an aspherical lens. Specifically, the preform 4 was disposed in the lower mold member 2 of the press mold composed of the lower mold member 2 and the upper mold member 1, and the atmosphere in the quartz tube 11 was replaced with a nitrogen atmosphere. Then, a heater (not shown) was energized to heat the inside of the quartz tube 11. The temperature inside the press die was set to a temperature at which the glass exhibited a viscosity of 10 ⁸ to 10 ¹⁰ dPa · s, while the upper mold member 1 moved the pressure rod l3 and pressed downward while this temperature was maintained. And the preform formed in the mold was pressed downward. The press was carried out for a press time of 30 seconds at a pressure of 8 MPa. After the press, the pressure in the press die was removed and while the glass molded product was in contact with the lower mold member 2 and the upper mold member 1 of the press mold, the glass molded product had a viscosity of 10 ¹² dPa · s. The mixture was slowly cooled to a temperature having a temperature, then quenched to room temperature, and taken out from the press die to obtain an aspherical lens having a concave meniscus shape.

In Fig. 1, reference numeral 3 designates a sleeve member, reference numeral 9 designates a support rod, reference numeral 10 designates a support bed, and reference numeral 14 designates a thermocouple.

In the same manner as described above, the preform obtained from the molten glass having the glass composition of Examples 1 to 37 was precision press-molded by the following method different from the above method. In this method, first, while the preform was suspended, the preform was preheated to a temperature at which the glass constituting the preform had a viscosity of 10 ⁸ dPa · s. Separately, the press mold having the upper mold member, the lower mold member and the sleeve member is heated to a temperature at which the glass exhibits a viscosity of 10 ⁹ to 10 ¹² dPa · s, and the preheated preform is introduced into the cavity of the press mold. And precision press molding at 10 MPa. Simultaneously with the press initiation, cooling of the glass and the press die begins, cooling continues until the molded glass has a viscosity of at least 10 ¹² dPa · s, and the molded article is taken out of the press mold to provide an aspherical lens. . The aspherical lens obtained by this method had a very high surface precision.

An anti-reflection film was formed on each of two types of aspherical lenses obtained by precision press molding.

In this way, a high precision optical element formed of high refractive index glass having excellent internal quality could be obtained with high productivity.

These optical elements are suitable for digital still cameras, digital video cameras, mobile phone mounted cameras, and the like.

[Industry availability]

According to the present invention, an optical glass having high refractive index, excellent glass stability, low glass transition temperature, and low temperature softening property suitable for precision press molding can be obtained, and a preform for precision press molding can be produced from the optical glass. In addition, optical elements such as various lenses and the like can be manufactured from such preforms.

According to the present invention, a high refractive optical glass having low temperature softening property suitable for precision press molding and excellent glass stability suitable for hot forming of a preform, a preform for precision press molding formed from the optical glass, a manufacturing process thereof, and the glass It is possible to provide an optical element formed therein and its manufacturing process.

Claims (10)

Expressed in mass%, B ₂ O ₃ 13-30%, Li ₂ O 0.1-4%, ZnO 17-35%, La ₂ O ₃ 15-45%, Ta ₂ O ₅ 4-15% (however, 15 % Excludes), ZrO ₂ 0-10%, Ta ₂ O ₅ / (Ta ₂ O ₅ + ZrO ₂ + Nb ₂ O ₅ )> 0.3, Nb ₂ O ₅ 0-10%, WO ₃ 0-20% And an optical glass having a refractive index (n _d ) of 1.80 to 1.84 and an Abbe's number (v _d ) of 40.0 to 45.0 and comprising Sb ₂ O ₃ 0-1%. According to claim 1, wherein the optical glass the total amount of Li ₂ 0 and Zn0 20 to 35% by weight. The method according to claim 1 or 2, expressed in mass%, Si0 ₂ 0 to 10%, Gd ₂ 0 ₃ 0 to 6% (except 6%), Y ₂ 0 ₃ 0 to 10%, Yb Optical glass further comprising ₂ 0 ₃ 0-10%. The method of claim 3, wherein B ₂ O ₃ , Li ₂ O, ZnO, La ₂ O ₃ , Ta ₂ 0 ₅ , ZrO ₂ , Nb ₂ 0 ₅ , WO ₃ , SiO ₂ , Gd ₂ O ₃ , Y ₂ 0 ₃ , Yb ₂ O ₃ and Sb ₂ 0 ₃ the total amount of the optical glass not less than 99% by weight of. The preform for precision press molding formed from the optical glass of any one of Claims 1-4. The preliminary molded body formed of the optical glass of any one of claims 1 to 4 in the process of flowing out the molten glass, separating the molten glass mass, and cooling the molten glass mass, Process for producing a preform for precision press molding comprising the step of molding. An optical element formed of the optical glass recited in any one of claims 1 to 4. An optical element comprising the step of heating the preform for precision press molding or the preform for precision press molding manufactured by the process of claim 6, and the step of precision press molding the preform for precision press molding with a press die. Manufacturing process. The process for manufacturing an optical element according to claim 8, wherein the preform for precision press molding is introduced into a press mold, and the preform for precision press molding and the press mold are heated together to perform precision press molding. 10. The process of claim 8, comprising heating the preform for precision press molding and introducing a heated preform for precision press molding into a press mold preheated to perform precision press molding.

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